Catalysis by single isolated atoms of precious metals has attracted much recent interest, as it promises the ultimate in atom efficiency. Most previous reports are on reducible oxide supports. Here we show that isolated palladium atoms can be catalytically active on industrially relevant g-alumina supports. The addition of lanthanum oxide to the alumina, long known for its ability to improve alumina stability, is found to also help in the stabilization of isolated palladium atoms. Aberration-corrected scanning transmission electron microscopy and operando X-ray absorption spectroscopy confirm the presence of intermingled palladium and lanthanum on the g-alumina surface. Carbon monoxide oxidation reactivity measurements show onset of catalytic activity at 40°C. The catalyst activity can be regenerated by oxidation at 700°C in air. The high-temperature stability and regenerability of these ionic palladium species make this catalyst system of potential interest for low-temperature exhaust treatment catalysts.

By means of first-principles computation, metal (Cu, Ag, Au, Pt, Rh, Pd, Fe, Co, and Ir) doped hexagonal boron nitride nanosheets (h-BNNSs) have been systematically investigated. The strong interaction between the metal atoms and defect sites in h-BNNS, such as the boron vacancy and nitrogen edge, suggests that metal doped h-BN nanosheets (M-BNNSs) should be stable under high temperatures. The catalytic activity of Co doped h-BNNS is also investigated by using CO oxidation as a probe, and the calculated low barrier suggests that the Co-BNNS is a viable catalyst for CO oxidation. Based on electronic structure analysis, the catalytic capacity of Co-BNNS is attributed to the strong mixing between the cobalt 3d orbitals and oxygen 2p orbitals, which activates the adsorbed molecular or atomic oxygen.

Plane-wave density functional theory calculations have been carried out to explore possible pathways in methanol steam reforming (MSR) on Cu(111). We focus on reactions involving the adsorbed formaldehyde intermediate (CH(2)O) produced by methanol decomposition and the surface hydroxyl (OH) species generated by dissociative adsorption of H(2)O. Several possible pathways leading to the H(2) + CO(2) products have been identified. The two most likely pathways involve the formate (CHOO), rather than the carboxyl (COOH), intermediate, and they possess barriers lower than that of the rate-limiting step of MSR, namely the dehydrogenation of adsorbed methoxyl (CH(3)O) species.

No abstract

The reactions of FeO + with H 2 , D 2 , and HD were studied in detail from 170 to 670 K by employing a variable temperature selected ion flow tube apparatus. High level electronic structure calculations were performed and compared to previous theoretical treatments. Statistical modeling of the temperature and isotope dependent rate constants was found to reproduce all data, suggesting the reaction could be well explained by efficient crossing from the sextet to quartet surface, with a rigid near thermoneutral barrier accounting for both the inefficiency and strong negative temperature dependence of the reactions over the measured range of thermal energies. The modeling equally well reproduced earlier guided ion beam results up to translational temperatures of about 4000 K.